Start out and trip (3,3)
I believe the answer is:
set off
This clue is a double definition.
'start out' is the first definition.
(I've seen this before)
'trip' is the second definition.
('set off' can be a synonym of 'trip')
'and' is the link.
(Other definitions for set off that I've seen before include "Begin journey or cause to explode" , "Leave - explode" , "Begin journey or cause to ignite" , "Counterbalance" , "Explode; start journey" .)